1. Field of the Invention
The present invention generally relates to motorcycle transmissions. More specifically, the present invention relates to final drive transmissions having flexible drive members secured in position by flexible drive member retention components.
2. Related Art
Motorcycles are often powered by internal combustion engines having output shafts. In some motorcycles, the output shaft is coupled to a final drive mechanism through a change speed transmission featuring a variety of gear ratios that can be selectively engaged. The output of the change speed transmission, in turn, drives an output pulley. Torque from the output pulley is transferred to an input pulley positioned on a rear wheel. A flexible drive member, such as a belt or chain for instance, preferably extends between the two pulleys.
The flexible drive member is susceptible to slipping during periods of rapid acceleration and deceleration. For instance, during a period of rapid acceleration, the output pulley is driving the wheel pulley. Accordingly, the flexible drive member slacks on the side of the pulleys moving in the direction from the wheel pulley to the output pulley. In addition, during rapid deceleration, the inertia of the rear wheel acts to drive the output pulley. Accordingly, the flexible drive member slacks on the side of the pulleys moving in the direction from the output pulley to the wheel pulley.
Because of the periodic slacking described above, the connection between the pulleys and the drive member can become unstable. For instances, the flexible drive member can skip relative to the pulley in a manner which effects the overall transfer of power between the engine and the rear wheel. In addition, as the flexible drive member slips relative to the pulleys, the flexible drive member can be thrown from the output pulley and disable the motorcycle. Thus, the vehicle will require frequent servicing to replace the flexible drive member on the pulleys. Moreover, the slackened portions of the flexible drive members can slap against other components of the motorcycle resulting in undue noise and unnecessary wear of both the flexible drive member and the components being slapped.
Accordingly, an improved mechanism for reducing the effects of flexible drive member slack in a motorcycle transmission is desired. Preferably, this mechanism includes retention members to maintain the relative positioning between a portion of the pulley and the flexible drive member during both acceleration and deceleration. Moreover, this arrangement preferably accommodates the tendency of the belt to be thrown forward by the drive pulley during rapid acceleration from a decelerated state to reduce accelerated wear on the retention members.
Accordingly, one aspect of the present invention involves a motorcycle transmission comprising a change speed transmission and a final drive. The change speed transmission has an input gear positioned on a first lateral side of the motorcycle transmission and an intermediate pulley positioned on a second lateral side of the motorcycle transmission. An output pulley of said change speed transmission is positioned on the first lateral side and is connected to an output shaft of the change speed transmission. The final drive comprises the output pulley of the change speed transmission, a driven pulley, and a flexible drive member extending around the output pulley and the driven pulley. The driven pulley is positioned rearward of the output pulley with at least one retaining member being positioned forward of the output shaft. The retaining member is capable of turning relative to a mounting shaft for the retaining member and comprises an outer contact surface. The flexible drive member is interposed between the outer contact surface and the output pulley. The flexible drive member is secured to the output pulley by the outer contact surface.
Another aspect of the present invention involves a motorcycle comprising an engine and a rear wheel. The engine is drivingly engaged to an output pulley with the output pulley being connected to an output shaft. The output shaft extends through a portion of a crankcase, and a final drive drivingly couples the output pulley and the rear wheel. The final drive comprises a flexible drive member that wraps around at least a portion of the output pulley. A rotary guide member is positioned forward of an axis of rotation of the output pulley. The flexible drive member passes between the rotary guide member and the output pulley such that the flexible drive member is substantially held in position on the output pulley by the rotary guide member.